1. Field of the Invention
The present invention relates to a dryer section apparatus for drying a web of paper. More specifically, the present invention relates to a dryer section apparatus which includes a single-tier group.
2. Information Disclosure Statement
A revolutionary concept in drying technology was disclosed in U.S. Pat. No. 4,934,067. The aforementioned '067 patent described a singe-tier drying group followed by an inverted single-tier group for drying the opposite side of the web. The aforementioned arrangement committed alternate sides of the web to be dried while maximizing the drying effect of each dryer within a dryer group.
However, in certain applications, it is desirable to reduce the overall length of the dryer section apparatus such being the case particularly when rebuilding a dryer section such that the building of additional mill space is avoided.
More specifically, on light-weight grade papers, the aforementioned arrangement of the '067 patent has achieved enormous commercial application. However, on heavier weight grades and board production, it has been discovered that sheet restraint will be particularly required only in the downstream or dry end of the dryer section. Such is the case because at the wet end or upstream end of the dryer section, although much of the water is removed at this end, comparatively little shrinkage takes place. Moreover, the majority of shrinkage takes place at the dry end or downstream end of the dryer section.
Accordingly, the present invention envisages the insertion of a two-tier dryer section between an upstream and a downstream single-tier group. Thus, reducing the overall length of the dryer section apparatus while maintaining the essential feature of cross machine directional restraint of the web at the dry end of the dryer section apparatus.
Accordingly, a primary objective of the present invention is the provision of the dryer section apparatus which overcomes the aforementioned problems associated with the prior art arrangement, and which makes a significant contribution to the art of drying a web of paper.
Another object of the present invention is the provision of a dryer section apparatus having a reduced overall length by the substitution of a two-tier dryer group between an upstream and a downstream single-tier group.
Other objects and advantages of the present invention will be readily apparent to those skilled in the art by consideration of the detailed description contained hereinafter, taken in conjunction with the annexed drawings.